Method for preparing a representation of a geographical polygon

ABSTRACT

A computer-implemented method including receiving a first representation of a geographical polygon defining a parcel of land, which first representation includes latitude and longitude coordinates that represent at least the corners of the geographical polygon; based on the first representation, determining various features of the geographical polygon; and preparing a second representation of the geographical polygon, which second representation includes the geometric centre of geographical polygon, first two alphanumeric characters, second two alphanumeric characters, a fifth alphanumeric character, and a sixth alphanumeric character.

TECHNICAL FIELD

The present invention relates to a computer-implemented method forpreparing a representation of a geographical polygon defining a parcelof land as shown on a digital satellite and/or aerial image. The presentinvention also relates to a computer program product, acomputer-readable storage medium, an electrical signal, and a computerdevice.

BACKGROUND

Geographical shapes (polygons) may be parcels of land on a map that arepixelated and used to represent real-estate, agricultural farms,forests, parks and other aggregated land assets. Communicating theextent of a geographical polygon is typically done by an array of GPScoordinates that represent the edges (vertices) of the polygon. Thearray of edge coordinates is represented digitally using a variety offile formats such as CSV, Shapefile, KML among others.

However, communicating the shape of a geographical polygon from oneentity to another (especially in offline mode) can be often hard becauseof the nature of information. While the traditional approach is the mostaccurate way to inform the shape of the geographical polygon, it rendersitself to not be user-friendly.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome or at leastalleviate the aforementioned problems.

According to a first aspect of the present invention, this and otherobjects is achieved by a computer-implemented method, which methodcomprises: receiving a first representation of a geographical polygondefining a parcel of land as shown on a digital satellite and/or aerialimage, which first representation includes latitude and longitudecoordinates that represent at least the corners (vertices) of thegeographical polygon; based on the first representation,

-   -   determining the geometric centre of the geographical polygon,    -   determining half the length of the geographical polygon in the        north-south direction and providing first two alphanumeric        characters XX representing the determined half-length of the        geographical polygon in the north-south direction,    -   determining half the width of the geographical polygon in the        east-west direction and providing second two alphanumeric        characters YY representing the determined half-width of the        geographical polygon in the east-west direction,    -   determining which shape of a preselected number of different        shapes that best matches the geographical polygon and retrieving        from a table a fifth alphanumeric character Z representing that        shape, and    -   determining a principal axis of the geographical polygon and        providing a sixth alphanumeric character A representing the        angle of the determined principal axis relative to the        north-south direction; and

preparing a second representation of the geographical polygon, whichsecond representation includes the geometric centre of geographicalpolygon, the first two alphanumeric characters, the second twoalphanumeric characters, the fifth alphanumeric character, and the sixthalphanumeric character.

By means of the present invention, it becomes possible to represent theparcel of land using much less data but with manageable loss inaccuracy*. This in turn facilitates communication of the whereabouts andextension of the parcel of land. For example, the first representationof a 15-corner geographical polygon defining the parcel of land maycontain at least 15×2×6=180 digits (the GPS coordinates of each cornerhere comprises two six-digit numbers), whereas the second representationof the same parcel of land may contain only (1×2×6)+2+2+1+1=18characters. This means for example that the second representation can betransmitted to a more basic cell phone (also referred to as a featurephone) using an SMS message limited to 160 characters, which indeed isuseful in communities where more advanced smartphones may not be readilyavailable. Also, a farmer can by means of the second representation(e.g. memorized or in the SMS message) easily communicate the(approximate) location and shape of their parcel of land to agenciessuch as banks, which are slowly using satellite imagery to analyse thecredit worthiness of a farmer.

In other words, the present invention may encode data (firstrepresentation of geographical polygon->second representation) forreliable and/or efficient transmission or storage (and correspondingdecoding).

*Initial tests have shown an average accuracy of 90% in representingmost geographical polygons.

Furthermore, as the algorithm of the present invention is quite“simple”/not resource-intensive, the second representation may beconstructed offline (i.e. without internet connection), which allows thepresent invention to be used also in remote rural areas where internetconnection may be absent or at least not stable.

The first representation of the geographical polygon could for examplebe provided by (manually) marking the corners of the parcel of land asshown on the digital satellite and/or aerial image of an electronicmapping service. Furthermore, the geometric centre of the geographicalpolygon, which may be referred to as the geographical polygon'scentroid, may for example be determined using geometric decomposition.Furthermore, the principal axis of the geographical polygon may be theaxis for which the product of inertia is zero.

Determining the geometric centre of the geographical polygon may includedetermining a latitude coordinate LatC and a longitude coordinate LongCrepresenting the geometric centre of the geographical polygon, whereinthe latitude coordinate and the longitude coordinate are included in thesecond representation of the geographical polygon. Hence, the secondrepresentation may be (LatC, LongC) [XX YY ZA], for example (57.7065,11.9687) [12 53 8 5]. Alternatively, the geometric centre of thegeographical polygon could in the second representation for example berepresented by three words as provided by what3words, which can make thesecond representation easier to remember. what3words has assigned each 3m square in the world a unique 3 word address, for example///save.strictly.pigment.

The method may further comprise rotating the geographical polygon sothat the determined principal axis aligns with the north-southdirection. This may facilitate and speed up determining the half-length,half-width, and/or which shape that best matches the geographicalpolygon.

Accordingly, said half the length and half the width may be determinedof the geographical polygon so rotated.

The first two alphanumeric characters XX representing the determinedhalf-length of the geographical polygon in the north-south direction maybe provided by dividing the determined half-length by the pixel size ofsaid digital satellite and/or aerial image, wherein the second twoalphanumeric characters YY representing the determined half-width of thegeographical polygon in the east-west direction are provided by dividingthe determined half-width by the pixel size of said digital satelliteand/or aerial image. As usually employed in the field of satellite oraerial imagery, the pixel size (resolution) of an image refers to thedistance covered on the ground by each of the pixels of the image. Thepixel size (resolution) of Sentinel satellite images may for example be30 m, which for an exemplary half-length of 500 m means that the firsttwo alphanumeric characters XX, in case they are digits 0-9, become500/30=17 (rounded to the nearest integer). The maximum half-length (andhalf-width) would here be 99*30=2970 m, which for the purpose ofagriculture usually is enough.

Determining which shape of a preselected number of different shapes thatbest matches the geographical polygon may include overlaying thedifferent shapes over the rotated geographical polygon to determinewhich of the different shapes that overlays the rotated geographicalpolygon in the most accurate way. Which of the different shapes thatoverlays the rotated geographical polygon in the most accurate way mayfor example be determined iteratively by looking at non-intersectionareas of the overlaid shapes and the geographical polygon. Thepreselected number of different shapes may for example include circle,rectangle, rhombus, triangle, ellipse, square, and trapezoid. These areshapes that can approximate most parcels of land/farms.

The first two alphanumeric characters, the second two alphanumericcharacters, the fifth alphanumeric character, and the sixth alphanumericcharacter may be digits, for example 0-9. Hence, an exemplary secondrepresentation may be (57.7065, 11.9687) [12 53 8 5].

Alternatively, at least the first two alphanumeric characters and thesecond two alphanumeric characters may be (Latin) letters. Hence,another exemplary second representation may be (57.7065, 11.9687) [RG AH8 5]. There are 26 letters in the English alphabet, which yields 26²=676different two-letter combinations, which in turn means that the maximumhalf-length (and half-width) can be increased to 676*30=20 km (for 30 mpixel size).

The fifth alphanumeric character and/or the sixth alphanumeric charactercould also be letters. This could improve the granularity.

The method may further comprise transmitting said second representationof the geographical polygon to an electronic device, for example in anSMS message to a cell phone, as mentioned above.

The method may further comprise displaying said second representation ofthe geographical polygon on a display, whereby it can be written down onpaper or memorized by a user (farmer). The display may for example bethe display of a computer device performing the present method.

The second representation could be transmitted and/or displayed as it is(i.e. as a phrase, for example (57.7065, 11.9687) [12 53 8 5]), orencoded as a QR code, for example.

The method may for example be performed by an app on a smartphone ortablet, typically using a processor and memory of the smartphone ortablet.

According to a second aspect of the invention, there is provided acomputer-implemented method, which method comprises: receiving a secondrepresentation of a geographical polygon, which second representation isprepared by the computer-implemented method according to the firstaspect; restoring the geographical polygon based on the secondrepresentation; and displaying the restored geographical polygonoverlaid on a digital satellite and/or aerial image. The method of thesecond aspect may be regarded as interrelated to the method of the firstaspect (first aspect: encoding—second aspect: decoding).

Restoring the geographical polygon based on the second representationmay basically include performing the algorithm of the first aspect ofthe invention in reverse. Furthermore, it should be appreciated that therestored geographical polygon may be an approximation of the originalgeographical polygon.

Furthermore, as the algorithm of the present invention is quite simple,the geographical polygon second representation may be restored offline(i.e. without internet connection), which allows the present inventionto be used also in remote rural areas where internet connection may beabsent or at least not stable.

Hence in this second aspect the farmer can come to the bank with justthe second representation, whereby the bank easily can see the farmer'sparcel of land on the digital satellite and/or aerial image, to forexample analyze the credit worthiness of the farmer.

According to a third aspect of the invention, there is provided acomputer program product comprising computer program code to perform,when executed on a computer device, the method according to the firstaspect and/or according to the second aspect. The computer programproduct may be a non-transitory computer program product. The computerdevice may for example be the aforementioned smartphone or tablet. Thecomputer program product may be an app.

According to a fourth aspect of the invention, there is provided acomputer-readable storage medium comprising the computer program productaccording to the third aspect.

According to a fifth aspect of the invention, there is providedelectrical signal embodied on a carrier wave and propagated on anelectrical medium, the electrical signal comprising the computer programproduct according to the third aspect.

According to a sixth aspect of the invention, there is provided acomputer device, for example a smartphone or tablet, configured toperform the method according to the first aspect and/or according to thesecond aspect. The computer device may be configured to perform themethod according to the first aspect and/or according to the secondaspect by means of an app. The app may run or be executed on thecomputer device using a processor and memory of the computer device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be describedin more detail, with reference to the appended drawings showing acurrently preferred embodiment of the invention.

FIG. 1 schematically illustrates i.a. a computer device according to anaspect of the present invention.

FIG. 2 is a flow chart of a method according to aspects of theinvention.

FIGS. 3 a-g illustrate various steps of the present method.

DETAILED DESCRIPTION

FIG. 1 illustrates a computer device 100 according to an aspect of thepresent invention. The computer device 100 is here a smartphone (e.g. aniPhone or an Android phone). Alternatively, the computer device 100could be a tablet (e.g. an iPad) or a laptop or a desktop computer.

The computer device 100 comprises an electronic display 102. Theelectronic display 102 may have a touchscreen, so that it except forshowing information can serve as a user input device. The computerdevice 100 may also comprise a processor 104, a memory 106, and astorage 108. The computer device 100 may also comprise a GPS receiver110 and wireless communication means 112.

Moving on, the computer device 100 may be configured to perform variousspecific steps or actions detailed in the following by means of an app114 (computer program product). The app 114 may be downloaded to thecomputer device 100 and stored on the aforementioned storage 108. Theapp 114 may run or be executed on the mobile computing device 10 usingthe aforementioned processor 104 and memory 106.

Turning to FIG. 2 , FIG. 2 is a flow chart of a method according to thefirst aspect (left) and the second aspect (right) of the presentinvention.

At S1, the method according to the first aspect comprises receiving afirst representation 10 of a geographical polygon 12 defining a parcelof land 14, as shown on a digital satellite and/or aerial image 16, seeFIG. 3 a . The parcel of land 14 may for example be an agriculturalfarm, but could alternatively be real-estate, forest, a park, etc. Thedigital satellite and/or aerial image 16 may for example be a Sentinelsatellite image. The first representation 10 includes latitude andlongitude coordinates Lat1-4, Long1-4 that represent the corners(vertices) 18 a-d of the geographical polygon 12. Here, the geographicalpolygon 12 is a (tilted) rectangle, but it could have any polygonalshape.

The first representation 10 of the geographical polygon 12 could beprovided by (manually) marking the corners 18 a-d of the parcel of land14 as shown on the digital satellite and/or aerial image 16 of anelectronic mapping service, at S0. For example, a user could mark thecorners 18 a-d as the digital satellite and/or aerial image 16 isdisplayed on the aforementioned electronic display 102 of the computerdevice (smartphone) 100, using a pointing device like their finger or astylus pen.

At S2, the method determines the geometric centre (centroid) 20 of thegeographical polygon 12, see FIG. 3 b . The geometric centre 20 of thegeographical polygon 12 may for example be determined using geometricdecomposition, a technique which is known per se. The geometric centre20 is preferably represented by a latitude coordinate LatC and alongitude coordinate LongC, for example 57.7065 and 11.9687.

At S3, the method determines a principal axis 22 of the geographicalpolygon 12, see FIG. 3 c . The principal axis 22 is the axis for whichthe product of inertia is zero. The orientation of the principal axis 22with respect to the centroidal coordinates LongC and LatC can beobtained using

$\theta_{p} = {\frac{1}{2}{\tan^{- 1}\lbrack \frac{2I_{LongCLatC}}{I_{LatC} - I_{LongC}} \rbrack}}$

where I_(LongC), I_(LatC), and I_(LongCLatC) represent the moments ofinertia about the east-west direction 30, moment of inertia about thenorth-south direction 24, and the product of inertia with respect toeast-west direction 30 and north-south direction 24, respectively. Theangle θ_(p) is measured positive counter clockwise from the centroidaleast-west direction 30. From the angle θ_(p), the angle θ with thenorth-south direction 24 may be derived.

The method at S3 further provides a (sixth) alphanumeric character Arepresenting the angle θ of the determined principal axis 22 relative tothe north-south direction 24. The alphanumeric character A may forexample be a digit 0-9, wherein A=0 represents 0 degrees and A=9represents 324 degrees. The alphanumeric character A may for example bederived using the formula A=(angle θ made with vertical axis 24clockwise)/36. Here, the angle θ is about 20 deg, whereby A=1.

At S4, the method may comprise rotating the geographical polygon 12 sothat the determined principal axis 22 aligns with the north-southdirection 24, see FIG. 3 d.

At S5, the method comprises determining half the length 26 of therotated geographical polygon 12 in the north-south direction 24, seeFIG. 3 e , wherein half the length is ½ the length of the principal axis22 that intersects rotated geographical polygon 12 at both ends. Themethod at S5 further provides (first) two alphanumeric characters XXrepresenting the determined half-length 26. The two alphanumericcharacters XX may be provided by dividing the determined half-length 26by the pixel size of the digital satellite and/or aerial image 16. Foran exemplary half-length 26 of 500 m given a pixel size of 30 m, the twoalphanumeric characters XX, in case they are digits 0-9, become500/30=17 (rounded to the nearest integer).

At S6, the method comprises determining half the width 28 of the rotatedgeographical polygon 12 in the east-west direction 30, see FIG. 3 f ,wherein half the width is ½ the length of an axis, which axis passesthrough the geometric centre 20 and is perpendicular to the principalaxis 22, that intersects rotated geographical polygon 12 at both ends.The method at S6 further provides (second) two alphanumeric charactersYY representing the determined half-width 28. The two alphanumericcharacters YY may be provided by dividing the determined half-width 28by the pixel size of the digital satellite and/or aerial image 16. Foran exemplary half-width 26 of 700 m given a pixel size of 30 m, the twoalphanumeric characters YY, in case they are digits 0-9, become700/30=23 (rounded to the nearest integer).

At S7, the method determines which shape of a preselected number ofdifferent shapes that best matches the (rotated) geographical polygon12, and retrieves from a table a (fifth) alphanumeric character Zrepresenting that shape. The table may for example be:

Z Shape 0 Circle 1 Rectangle 2 Rhombus 3 Triangle 4 Ellipse 5 Square 6Trapezoid 7 Reserved 8 Reserved 9 Reserved

Specifically, determining which shape of that best matches thegeographical polygon 12 may include overlaying the different shapes ofthe table, which overlaid shapes are adjusted based on the determinedhalf-length 26 and half-width 28, over the rotated geographical polygon12 to determine which of the different shapes that overlays the rotatedgeographical polygon 12 in the most accurate way. Namely, each overlaidand adjusted shape is rotated about the centroid, and for each rotation,the area not intersecting between the shape and the polygon 12 isestimated. The method thus derives areas not intersected for allrotation possibilities and shapes of the table. Given seven shapes as inthe table above, and 36 different rotation angels, it results in 252possibilities. Then, the shape with the least area lost duringintersection is selected. Here, the most representative shape is arectangle 32 (see FIG. 3 g ), which yields Z=1.

At S8, the method prepares a second representation of the geographicalpolygon, which second representation includes the geometric centre ofgeographical polygon (here LatC, LongC), the first two alphanumericcharacters XX, the second two alphanumeric characters YY, the fifthalphanumeric character Z, and the sixth alphanumeric character A. Hence,the second representation may be (LatC, LongC) [XX YY ZA], for example(57.7065, 11.9687) [17 23 1 1].

At S9, the method may comprise transmitting the second representation 34of the geographical polygon 12 to an electronic device 200, see FIG. 1 .The second representation may for example be transmitted in an SMSmessage using the wireless communication means 112 of the computerdevice 100. The receiving electronic device 200 may be a feature phone.

Alternatively or complementary, the second representation may bedisplayed on the electronic display 102 of the computer device 100(S10).

At S11, the method according to the second aspect of the inventioncomprises receiving the second representation 34 of the geographicalpolygon 12, by the computer device 100 or by another similar computerdevice 100′ running the same app 114, see FIG. 1 . The secondrepresentation 34 (e.g. (57.7065, 11.9687) [17 23 1 1]) may for examplebe manually entered into the computer device 100′.

At S12, the method further comprises restoring the geographical polygon12 based on the second representation 34, by performing steps S2-S8 “inreverse”. That is, the method may derive the shape defined by Z, adjustthe half-length and half-width according to XX and YY, respectively,rotate the shape based on A, and the position the shape based on LatCand LongC.

At S13, the method displays the restored geographical polygon 12′overlaid on a digital satellite and/or aerial image on the electronicdisplay 102 of the computer device 100′, see FIG. 1 . Hence, the parcelof land 14 can easily be identified on the digital satellite and/oraerial image.

In an exemplary use case of the present invention, a farmer can come toan agency or bank hosting the computer device 100 and—possibly with thehelp of a specialist—identify their parcel of land 14 on the digitalsatellite and/or aerial image 16, which allows for the provision offirst representation 10. The computer device 100 then prepares thesecond representation 34 based on the first representation 10, and SMSsthe second representation 34 to the farmer's feature phone. The farmermay then go to another agency or bank bringing the feature phone withhim and present the second representation 34 to the another agency orbank, which then performs reconstruction using another computer device100′, allowing the parcel of land 14 to be displayed and identifieddigital satellite and/or aerial imagery, which in turn for example canbe used to analyze the credit worthiness of the farmer. It is expectedthat the present invention can be of great use for farmers especially inthe developing world.

The person skilled in the art realizes that the present invention by nomeans is limited to the embodiments described above. On the contrary,many modifications and variations are possible within the scope of theappended claims.

1. A computer-implemented method, comprising: receiving a firstrepresentation of a geographical polygon defining a parcel of land asshown on a digital satellite and/or aerial image, the firstrepresentation including latitude and longitude coordinates (Lat1-4;Long1-4) that represent at least corners of the geographical polygon;based on the first representation, determining a geometric centre of thegeographical polygon, determining half a length of the geographicalpolygon in a north-south direction and providing first two alphanumericcharacters (XX) representing the determined half-length of thegeographical polygon in the north-south direction, determining half awidth of the geographical polygon in an east-west direction andproviding second two alphanumeric characters (YY) representing thedetermined half-width of the geographical polygon in the east-westdirection, determining which shape of a preselected number of differentshapes that best matches the geographical polygon and retrieving from atable a fifth alphanumeric character (Z) representing that shape, anddetermining a principal axis of the geographical polygon and providing asixth alphanumeric character (A) representing an angle (θ) of thedetermined principal axis relative to the north-south direction; andpreparing a second representation of the geographical polygon, whichsecond representation includes the geometric centre of the geographicalpolygon, the first two alphanumeric characters, the second twoalphanumeric characters, the fifth alphanumeric character, and the sixthalphanumeric character.
 2. The computer-implemented method according toclaim 1, wherein determining the geometric centre of the geographicalpolygon includes determining a latitude coordinate (LatC) and alongitude coordinate (LongC) representing the geometric centre of thegeographical polygon, and wherein the latitude coordinate and thelongitude coordinate are included in the second representation of thegeographical polygon.
 3. The computer-implemented method according toclaim 1, which method further comprises rotating the geographicalpolygon so that the determined principal axis aligns with thenorth-south direction.
 4. The computer-implemented method according toclaim 3, wherein said half the length and half the width are determinedof the geographical polygon so rotated.
 5. The computer-implementedmethod according to claim 1, wherein the first two alphanumericcharacters (XX) representing the determined half-length of thegeographical polygon in the north-south direction are provided bydividing the determined half-length by a pixel size of said digitalsatellite and/or aerial image, and wherein the second two alphanumericcharacters (YY) representing the determined half-width of thegeographical polygon in the east-west direction are provided by dividingthe determined half-width by the pixel size of said digital satelliteand/or aerial image.
 6. The computer-implemented method according toclaim 3, wherein determining which shape of a preselected number ofdifferent shapes that best matches the geographical polygon includesoverlaying the different shapes over the rotated geographical polygon todetermine which of the different shapes that overlays the rotatedgeographical polygon in a most accurate way.
 7. The computer-implementedmethod according to claim 1, wherein the first two alphanumericcharacters, the second two alphanumeric characters, the fifthalphanumeric character, and the sixth alphanumeric character arenumerical digits.
 8. The computer-implemented method according to claim1, wherein the first two alphanumeric characters and the second twoalphanumeric characters are letters.
 9. The computer-implemented methodaccording to claim 1, which method further comprises transmitting saidsecond representation of the geographical polygon to an electronicdevice.
 10. The computer-implemented method according to claim 1, whichmethod further comprises displaying said second representation of thegeographical polygon on a display.
 11. The computer-implemented methodaccording to claim 1, performed by an app on a smart phone or tablet.12. A computer-implemented method, comprising: receiving a secondrepresentation of the geographical polygon, which second representationis prepared by the computer-implemented method according to claim 1;restoring the geographical polygon based on the second representation;and displaying the restored geographical polygon overlaid on the digitalsatellite and/or aerial image.
 13. A computer program product comprisingcomputer program code to perform, when executed on a computer, themethod according to claim
 1. 14. A non-transitory computer-readablestorage medium comprising the computer program product according toclaim
 13. 15. An electrical signal embodied on a carrier wave andpropagated on an electrical medium, the electrical signal comprising thecomputer program product according to claim
 13. 16. A computer device,configured to perform the method according to claim
 1. 17. The computerdevice of claim 16 being a smart phone or a tablet.